In the honing field or more generally the abrading field of sizing internal diameters, an inprocess plug gaging device is sometimes used to check the size of a bore based on a go-no-go gaging procedure. Such gaging devices are shown in the prior art to patents to Calvert, U.S. Pat. Nos. 2,741,071; Gross, 2,787,865 and 2,787,866; Seaborg, 2,870,577; Greenberg, 3,286,409. All of these patents show the operation of a honing machine wherein the plug gage will attempt to enter the bore during each reciprocating cycle of the honing apparatus, i.e., the hone will be rotated and reciprocated the length of the bore. As long as the honing operation is in progress and the plug cannot enter, the abrading machining process will continue. As soon as the plug is capable of entering the bore being honed, the machine will detect the entrance of the plug into the bore which signals that the bore has been machined to size, and the machine will then retract the abrading tool from the bore and shut down. All of the gaging elements in these patents use a biasing member to urge the plug gage into the bore which is being machined. All use some type of switch member to detect when the plug has entered the bore, and all gage the hole size on each reciprocation of the honing tool.
Also in the prior art are gages which use a tapered gaging surface so that the gage will enter the bore a little amount each time the honing stroke reciprocates. This tapered gage will eventually gage the bore to the proper diameter, be sensed by a switch of some type and discontinue the honing operating. The major difference is that a straight gage has a chamfer at its leading edge and once the gage can enter, it usually will go in all the way and terminating the honing operation.
Some honing machines manufactured by the assignee of the invention have used the type of in-process gaging just described. In addition, some gaging processes have used a timed sequenced operation for holding the plug gage out of the bore for a finite period of time and then allow the gage to enter the bore near the end of the time cycle. In most cases the time of honing is approximately known and a timing mechanism is used to hold the gage out for 80% of the cycle and allow it to try to enter for approximately 20% of the cycle. This has the obvious advantage of extending the life of the gage member.
Our invention operates with a new style of abrading tools, sometimes known as microsizing tools and shown in a patent to co-inventor Fitzpatrick, U.S. Pat. No. 4,173,852. These tools are constructed from a continuous cylinder having abrasive particles secured onto the sleeve member to provide the cutting section for the process. The sleeve member is usually spirally grooved or slotted so that the diameter of the member is adjustable by an inner tapered surface of the tool body sliding on a tapered arbor on the tool shaft. These tools are generally used in an application where it is only necessary to pass and retract the tool through the bore in a single cycle. That is, the tool would enter the bore on the first pass, go completely through and then on the retracting pass, go through the bore a second time and that would complete the machining operation. In these types of machining processes, a gaging plug is mounted directly behind the abrading tool, and the bore diameter can be checked each time the tool is cycled through a workpiece. That is, the gage can enter or at least attempt to enter, the hole or bore that is being machined; and if it does enter, the tool size is within tolerance. Because of the nature of this type of operation, excessive wear will occur since the plug gage is used on every cycle in the same manner as that described in the prior art patents.
One of the objects of our invention is to retain the plug gage out of contact with the workpiece bore until a predetermined number of parts have been machined; then allow the plug gage to attempt to enter the bore on the next cycle of the machine. If the plug gage cannot enter the bore then the machine will be stopped, and the diameter of the tool can be adjusted and the operation continued.
Another object of this invention is to have the plug gage member retained out of contact with the workpiece bore and drop by gravity feed to check the bore on selective parts.
It is also an object of this invention to have a switch means detect the entrance of the plug a predetermined distance into the workpiece.
It is further the object of this invention to have a biasing means associated with the plug gage means and a spacer between the abrading tool element and the plug gage to retain the gage displaced from the tool element. Such a spacer would maintain the plug gage out of the bore until such time as the stroke of the spindle is increased whereby the plug gage can then attempt to enter the bore.
It is further the object of this invention to have a switch means sense a plug gage with biasing means to to continue or terminate the function of the machine.
In summary, the invention is an apparatus and method for gaging the cross-sectional diameter of a bore during an in-process operation of an abrading machine having gage means operatively supported on the abrading tool. The gage size is fixed to a predetermined diameter and held out of contact with the workpiece. This gaging means would attempt to enter the bore being machined at selected intervals or cycles at a predetermined part sampling rate and failure of the plug gage to enter the bore would indicate that the tool has been worn to the low tolerance or to an undersize condition. The invention further has a switch means for sensing proper size of the bore to continue operation of the machine if the plug has entered the workpiece a predetermined distance. In other words, if the plug gage enters the bore, the tool is properly sized. If the gage does not enter the bore, the tool is now undersize and should be readjusted. This method is called by the inventors tool sizing by unplug gaging.
The objects, features and advantages of the present invention are readily apparent from the following description of the best mode for carrying out the invention taken in connection with the accompanying drawings.